frontend-svelte/src/shared/api/queryClient.ts

import { QueryClient } from '@tanstack/query-core';

/**
 * TanStack Query client instance
 *
 * Configured for optimal caching and refetching behavior.
 * Used by all font stores for data fetching and caching.
 *
 * Cache behavior:
 * - Data stays fresh for 5 minutes (staleTime)
 * - Unused data is garbage collected after 10 minutes (gcTime)
 * - No refetch on window focus (reduces unnecessary network requests)
 * - 3 retries with exponential backoff on failure
 */
export const queryClient = new QueryClient({
    defaultOptions: {
        queries: {
            /**
             * Data remains fresh for 5 minutes after fetch
             */
            staleTime: 5 * 60 * 1000,
            /**
             * Unused cache entries are removed after 10 minutes
             */
            gcTime: 10 * 60 * 1000,
            /**
             * Don't refetch when window regains focus
             */
            refetchOnWindowFocus: false,
            /**
             * Refetch on mount if data is stale
             */
            refetchOnMount: true,
            /**
             * Retry failed requests up to 3 times
             */
            retry: 3,
            /**
             * Exponential backoff for retries
             * 1s, 2s, 4s, 8s... capped at 30s
             */
            retryDelay: attemptIndex => Math.min(1000 * 2 ** attemptIndex, 30000),
        },
    },
});